the d15 has a 5.276 stock rod length... the d16 has a 5.394 stock rod length... the compression heights are 1.213 and 1.161...
nobody says you have to keep those the same...
the stroke changes the CR when the piston is kept the same.. i think that the pin diameter is the same (19mm) ... so they will fit on the rod .. but if the CR was calculated for a 1.6 it wont be the same on a 1.5 crank...
d16 rods have a 1.89" big end bore for the crank and d15 rods have a 1.772" .... so.. they wont fit ..
have you already bought the parts?
you should call endyn (
www.theoldone.com) for your rods/pistons.... they should be able to help you .. i think they even have some custom sized rods .. to get you closer to oh so desirable ~1.75:1 rod:stroke ratio.... of which Larry Widmer (Endyn owner) knows quite a bit as he is running a de-stroker moldex crank and extra long rods in his 11s daily driver...